"I read a number of years ago that the proven executions of innocents in the US in the 20th Century is (approximately) 45 people. That's 45 innocent human beings who were premeditatedly murdered by the government."

If that is true, it's a pretty insignificant number- one person for every two years of last Century. Compare this to number of murders released by US governments, which resulted in that murderer killing again.
I don't know the numbers off hand, but:
According to this In Detroit:
"At least 1,085 people freed under the administrative release program in the last three years have been rearrested and charged with committing new crimes, a Detroit News investigation found.
Twelve have been convicted of murders committed after their release, three were convicted of manslaughter and eight more are awaiting trial on murder charges. In addition, the released suspects have committed at least 46 armed robberies, 40 violent assaults, 11 rapes and 14 carjackings. Their other crimes included robberies, burglaries, car theft, illegal weapons and drug dealing."
http://www.detnews.com/specialreports/2002/jail/a01-458845.htm

So in a time period of 3 years, in one city, and we can assume that not all were caught. 15 convicted of murder or manslaughter, with 11 awaiting the results of their trial [and they killed at least one person].
So in 3 years say 26 [at least] innocents killed in one city by people who had already been caught, tried, and served prison whatever time they did] compared to 1-2 killed in the entire nation who some have claimed they were innocent of the crime they are accused of committing.

Now were these "45 innocent human beings" over a century of time *really* innocent? Does innocent mean like OJ Simpson was innocent- in other words had these people had better defense lawyers could they have not faced the death penalty. Or was it a matter of their being technical errors in the trial. Were they part of some crime, but in the case that they were tried weren't actually the one who actually pulled the trigger- maybe due to the fact they didn't want to finger the real killer.
In other words, are these 45 truly innocent- had nothing to do with that particular murder or any other murder and criminal activity. Are the "45 innocent human beings" akin the Mob leaders, who though were responsible for many murders, were actually convicted for tax evasion, etc.

Or were these "45 innocent human beings" actually more like the victims of these 26 murderers in Detroit over a period of 3 years? Such as storekeepers, cops, someone going home from work, etc.